User manual

4200 User Manual Edgewater Networks, Inc.
Version 2.2 31
your IT administrator or service provider can usually provide these values. Some
typical examples are as follows:
WAN Link
WAN Downstream Bandwidth
WAN Upstream Bandwidth
T1
1.544Kbps
1.544Kpbs
SDSL
768Kbps
768Kbps
ADSL
Example 1 - 768Kbps
Example 1 - 256Kbps
Example 2 - 512Kbps
Example 2 - 128Kbps
Optionally enable priority IP addresses
VoIP traffic from devices that use the VoIP ALG function (phones, video stations,
softphones on Pcs, etc.) are already marked as high priority and do not need to be
manually configured in this list. This list is used to prioritize voice traffic from trunk
interfaces of IP PBXs or other high priority devices that do not use the VoIP ALG
function of the 4200.
E. Enter the IP address of other high priority devices in the priority IP
Addresses box.
You can enter individual IP addresses or a range using by appending a “-“ character
to the last octet. For example, 10.10.10.2-5 would specify 10.10.10.2, 10.10.10.3,
10.10.10.4 and 10.10.10.5 as voice devices.
WARNING: Care must be taken to ensure that the IP addresses entered do
not include data devices such as PCs or workstations. Traffic from these
devices will be placed in the priority voice queue internal to the 4200 and
burst up to full line rate. This will starve actual voice devices by
consuming priority bandwidth and result in dropped calls, busy signals &
poor voice quality.
Enable CAC
The 4200 uses CAC to limit the number of active voice calls over the WAN link. This
is necessary because a typical installation uses a ratio of 1:2 or 1:4 active voice calls
to voice devices on the assumption that 50% or 25% of all users are on the phone at
the same time. These ratios are guidelines only and at times the number of
concurrent calls may exceed the amount of WAN bandwidth available to process the
calls. In this instance existing phone calls will experience poor quality or be dropped
all together. To prevent this from occurring a typical voice installation will set a
threshold for the maximum number of concurrent voice calls supported by the WAN
access link. New call requests in excess of this threshold will receive the equivalent
of a “fast busy” and the WAN link will not become oversubscribed.
For IP Centrex installations the maximum number of concurrent voice calls is usually
configured in the 4200 by enabling CAC. When the 4200 is deployed in IP PBX
applications the maximum number of concurrent calls could be configured in the IP
PBX. If the PBX is responsible for this setting you do not need to configure CAC in
the 4200. Please check with your IT administrator to determine if this is the case.
PLEASE note that CAC is available in the 4200 for the MGCP and SIP VoIP protocols
only.